1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, more particularly to an electrophotographic photosensitive member having a low molecular weight organic photoconductive material which gives improved electrophotographic characteristics.
2. Related Background Art
In recent years, a large number of electrophotographic photosensitive members by use of organic compounds as the photoconductive member have been developed. Among them, most have the form of the photoconductive member separated in function into the charge generating substance and the charge transporting substance.
However, these photosensitive members have been generally regarded to have a great drawback of low durability as compared with inorganic photosensitive members. Durability may be classified broadly into durability in aspect of electrophotographic properties such as sensitivity, residual potential, charging ability, fuzzy image, etc. and mechanical durability such as abrasion, damage, etc. on the photosensitive member surface caused by sliding. Concerning durability in aspect of electrophotographic properties, it has been caused mainly by deterioration of the charge transporting material containing in the surface layer of the photosensitive member with ozone generated by corona discharging, NOx or photoirradiation.
As the organic charge transporting material, there have been proposed a large number of compounds such as hydrazone compounds as disclosed in U.S. Pat. No. 4,150,987, triazolepyrazoline compounds as disclosed in U.S. Pat. No. 3,837,851, stilbene compounds as disclosed in Japanese Patent Laid-open Application No. 58-198043, benzidine compounds as disclosed in Japanese Patent Laid-open Application Nos. 59-295558 and 62-201447, and considerable improvements are being done, but not satisfactorily under the present situation.
Further, in recent years, a new problem of a resting memory phenomenon of photosensitive members has been pointed out as the durable life of photosensitive members is improved and the image quality is made higher. The resting memory phenomenon refers to one which is basically of the deterioration caused by the corona products, in which rotation of the photosensitive member after completion of copying stops, and the charging ability at the portion stopped near the corona charger is lowered, whereby the image density is lowered only at that portion in the case of normal developing or elevated in the case of reversal developing. This phenomenon is liable to occur after the photosensitive member has been used for a long term, and is now becoming a serious problem as the photosensitive member life is elongated in recent years.